ma·zae·di·um 
(mə-zēdē-əm)
(mə-zēdē-əm)n. pl. ma·zae·di·a (-dē-ə)
A fruiting body of some lichens in which the spores lie freely in a powdery mass that is enclosed in a peridium.
[New Latin : Greek maza, lump; see mag- in the Appendix of Indo-European roots + Latin aedēs, house.]